1. Field of the Invention
The present invention relates to pacer housings and more particularly to those parts of the housing intended for connection to the electrode leads.
2. Description of the Prior Art
Implantable pacers normally have a pacer housing (also called can) containing electronic circuitry and a unit for electric power as well as different electrodes which are connected to the interior parts in the pacer housing and which are to be implanted in or in the vicinity of the heart. The electrodes are connected to the pacer by means of leads. The internal parts of the pacers have to be well protected against the internal environment, especially the body fluids in the body for a long period of time, which places strict requirements on all entries into the interior of the can and especially on the connections of the leads to the housing. At the same time it should be possible to disconnect the pacer from the implanted leads for replacement or servicing of the pacer. The connective parts of the pacer and the leads have largely been standardized so as to encompass a relatively deep female socket comprising a number of contact surfaces whereas the leads are provided with a male part comprising one or several corresponding peripheral, generally circular contact surfaces.
At present the connective part of the pacer housing containing the female socket is made of a transparent material, normally epoxy resin, which is molded onto the housing and onto contacts extending outwardly from the housing. The male part of the leads is normally locked by means of set-screws, although other fastening means have been envisaged. The positioning and alignment of the different contact surfaces and of the fastening means or metallic threads for the set screws prior to the molding of the connective part is however very complicated and the delay in the manufacturing process incurred by the curing of the epoxy resin is considerable.
It would thus be desirable if the molding procedure could be dispensed with.
It has been discussed that these complexities could be avoided by designing the pacer with a socket located inside the metal housing. This kind of socket, sometimes termed xe2x80x9cblack holesxe2x80x9d, is not used at present.
U.S. Pat. Nos 4,934,366 and 5,324,111, the teachings of both of which are incorporated herein by reference, describe two interior sockets or black holes for pacers. Both designs have a tubular member formed by a number of alternating sections made of metal and insulating ceramic, respectively. An end section of metal can be welded or bonded to an opening in the pacer housing by means of a flange. The use of different materials, however, sets high standards in regard of precision and durability of the component parts and as well as on the assembly procedure thereof. This is especially important since the interior sockets must meet very high standards regarding the integrity of the interior of the pacer housing during long times of implantation in a demanding environment. The manufacture of these known sockets thus is relatively complicated. The same is true for the device disclosed in U.S. Pat. No. 4,262,982, a ceramic socket combined with a metal flange for welding to a pacer housing and with a metallic interior contact pin. This device also has locking means in the form of an inwardly directed, circumferential rib located adjacent the opening of socket. This rib is intended to cooperate with barb-shaped sealing rings on the contact plug on the proximal end of the lead or catheter.
It is an object of the invention to provide a pacer housing which allows the molding procedure to be avoided and the design of an interior socket to be simplified to a high degree while still meeting the required high standards
The above object is achieved in accordance with the principles of the present invention in a pacemaker housing having a connector arrangement which is adapted to receive a contact plug at the proximal end of a lead, the pacemaker housing having a housing enclosure made of metal and the connector arrangement forming a tubular member with two opposite ends disposed inside of the housing. A first end of the tubular member is open and is welded or bonded to an opening in the wall of the housing. The second end of the tubular member is closed. The tubular member is made of metal that is weldable or bondable to the metal housing. The tubular member is structurally intact along its entire length. A number of interior components, adapted for mechanical and electrical contact with contact surfaces of the contact plug of the lead, are held in an insulating ceramic plug which is located in the interior of the tubular member and is coaxial therewith.